Accretion geometry of the black-hole binary Cygnus X-1 from X-ray polarimetry

M. Chauvin, H. G. Florén, M. Friis, M. Jackson, T. Kamae, Jun Kataoka, T. Kawano, M. Kiss, V. Mikhalev, T. Mizuno, N. Ohashi, T. Stana, H. Tajima, H. Takahashi, N. Uchida, M. Pearce

    Research output: Contribution to journalLetter

    3 Citations (Scopus)

    Abstract

    Black hole binary (BHB) systems comprise a stellar-mass black hole and a closely orbiting companion star. Matter is transferred from the companion to the black hole, forming an accretion disk, corona and jet structures. The resulting release of gravitational energy leads to the emission of X-rays1. The radiation is affected by special/general relativistic effects, and can serve as a probe for the properties of the black hole and surrounding environment, if the accretion geometry is properly identified. Two competing models describe the disk–corona geometry for the hard spectral state of BHBs, based on spectral and timing measurements2,3. Measuring the polarization of hard X-rays reflected from the disk allows the geometry to be determined. The extent of the corona differs between the two models, affecting the strength of the relativistic effects (such as enhancement of the polarization fraction and rotation of the polarization angle). Here, we report observational results on the linear polarization of hard X-ray emission (19–181 keV) from a BHB, Cygnus X-14, in the hard state. The low polarization fraction, <8.6% (upper limit at a 90% confidence level), and the alignment of the polarization angle with the jet axis show that the dominant emission is not influenced by strong gravity. When considered together with existing spectral and timing data, our result reveals that the accretion corona is either an extended structure, or is located far from the black hole in the hard state of Cygnus X-1.

    Original languageEnglish
    Pages (from-to)652-655
    Number of pages4
    JournalNature Astronomy
    Volume2
    Issue number8
    DOIs
    Publication statusPublished - 2018 Aug 1

    Fingerprint

    polarimetry
    geometry
    coronas
    polarization
    x rays
    relativistic effects
    time measurement
    companion stars
    linear polarization
    stellar mass
    accretion disks
    confidence
    alignment
    gravitation
    augmentation
    probes
    radiation

    ASJC Scopus subject areas

    • Astronomy and Astrophysics

    Cite this

    Chauvin, M., Florén, H. G., Friis, M., Jackson, M., Kamae, T., Kataoka, J., ... Pearce, M. (2018). Accretion geometry of the black-hole binary Cygnus X-1 from X-ray polarimetry. Nature Astronomy, 2(8), 652-655. https://doi.org/10.1038/s41550-018-0489-x

    Accretion geometry of the black-hole binary Cygnus X-1 from X-ray polarimetry. / Chauvin, M.; Florén, H. G.; Friis, M.; Jackson, M.; Kamae, T.; Kataoka, Jun; Kawano, T.; Kiss, M.; Mikhalev, V.; Mizuno, T.; Ohashi, N.; Stana, T.; Tajima, H.; Takahashi, H.; Uchida, N.; Pearce, M.

    In: Nature Astronomy, Vol. 2, No. 8, 01.08.2018, p. 652-655.

    Research output: Contribution to journalLetter

    Chauvin, M, Florén, HG, Friis, M, Jackson, M, Kamae, T, Kataoka, J, Kawano, T, Kiss, M, Mikhalev, V, Mizuno, T, Ohashi, N, Stana, T, Tajima, H, Takahashi, H, Uchida, N & Pearce, M 2018, 'Accretion geometry of the black-hole binary Cygnus X-1 from X-ray polarimetry', Nature Astronomy, vol. 2, no. 8, pp. 652-655. https://doi.org/10.1038/s41550-018-0489-x
    Chauvin, M. ; Florén, H. G. ; Friis, M. ; Jackson, M. ; Kamae, T. ; Kataoka, Jun ; Kawano, T. ; Kiss, M. ; Mikhalev, V. ; Mizuno, T. ; Ohashi, N. ; Stana, T. ; Tajima, H. ; Takahashi, H. ; Uchida, N. ; Pearce, M. / Accretion geometry of the black-hole binary Cygnus X-1 from X-ray polarimetry. In: Nature Astronomy. 2018 ; Vol. 2, No. 8. pp. 652-655.
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    abstract = "Black hole binary (BHB) systems comprise a stellar-mass black hole and a closely orbiting companion star. Matter is transferred from the companion to the black hole, forming an accretion disk, corona and jet structures. The resulting release of gravitational energy leads to the emission of X-rays1. The radiation is affected by special/general relativistic effects, and can serve as a probe for the properties of the black hole and surrounding environment, if the accretion geometry is properly identified. Two competing models describe the disk–corona geometry for the hard spectral state of BHBs, based on spectral and timing measurements2,3. Measuring the polarization of hard X-rays reflected from the disk allows the geometry to be determined. The extent of the corona differs between the two models, affecting the strength of the relativistic effects (such as enhancement of the polarization fraction and rotation of the polarization angle). Here, we report observational results on the linear polarization of hard X-ray emission (19–181 keV) from a BHB, Cygnus X-14, in the hard state. The low polarization fraction, <8.6{\%} (upper limit at a 90{\%} confidence level), and the alignment of the polarization angle with the jet axis show that the dominant emission is not influenced by strong gravity. When considered together with existing spectral and timing data, our result reveals that the accretion corona is either an extended structure, or is located far from the black hole in the hard state of Cygnus X-1.",
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    AU - Florén, H. G.

    AU - Friis, M.

    AU - Jackson, M.

    AU - Kamae, T.

    AU - Kataoka, Jun

    AU - Kawano, T.

    AU - Kiss, M.

    AU - Mikhalev, V.

    AU - Mizuno, T.

    AU - Ohashi, N.

    AU - Stana, T.

    AU - Tajima, H.

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    AU - Uchida, N.

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    AB - Black hole binary (BHB) systems comprise a stellar-mass black hole and a closely orbiting companion star. Matter is transferred from the companion to the black hole, forming an accretion disk, corona and jet structures. The resulting release of gravitational energy leads to the emission of X-rays1. The radiation is affected by special/general relativistic effects, and can serve as a probe for the properties of the black hole and surrounding environment, if the accretion geometry is properly identified. Two competing models describe the disk–corona geometry for the hard spectral state of BHBs, based on spectral and timing measurements2,3. Measuring the polarization of hard X-rays reflected from the disk allows the geometry to be determined. The extent of the corona differs between the two models, affecting the strength of the relativistic effects (such as enhancement of the polarization fraction and rotation of the polarization angle). Here, we report observational results on the linear polarization of hard X-ray emission (19–181 keV) from a BHB, Cygnus X-14, in the hard state. The low polarization fraction, <8.6% (upper limit at a 90% confidence level), and the alignment of the polarization angle with the jet axis show that the dominant emission is not influenced by strong gravity. When considered together with existing spectral and timing data, our result reveals that the accretion corona is either an extended structure, or is located far from the black hole in the hard state of Cygnus X-1.

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